eLife assessment
The analysis of 89,000 independent somatic mtDNA mutations provides compelling evidence that allows the authors to refute the idea that reactive oxygen species (ROS) are a main driver of mtDNA mutagenesis, although ROS effects may still be tissue-dependent. These are fundamental results with convincing evidence, and they should appeal to a broad audience. The discovery of transversion mutations (C>A/G>T and C>G/G>C), which previously were assumed to be almost nonexistent, will nevertheless require additional validation.